1. Field of the Invention
This invention relates to a process for preparing a hydroperoxide, more particularly it relates to a process for preparing a hydroperoxide by autoxidizing secondary alkyl group-substituted methylbenzenes.
2. Description of the Prior Art
Hydroperoxide prepared by autoxidizing secondary alkyl group-substituted methylbenzenes is useful as a starting material for preparing an alkyl-substituted phenol, particularly a methyl-substituted phenol. Secondary alkyl-group-substituted methylbenzenes, for example 3,5-dimethyl-isopropylbenzen (3,5-dimethyl cumene) is autoxidized to give the tertiary hydroperoxide and primary hydroperoxide as illustrated below. ##STR1##
The tertiary hydroperoxide is subjected to acid decomposition reaction to obtain a methyl substituted phenol, for example, 3,5-xylenol, and the primary hydroperoxide undergoes decomposition to give a methyl secondary alkyl phenol for example, 3-methyl-5-isopropylphenol.
It has been heretofore well known that tertiary hydroperoxide is prepared by autoxidizing secondary alkyl group-substituted benzenes, for example isopropylbenzene (cumene) and it is obtained in high yield and high selectivity. However, in case of secondary alkyl group-substituted methylbenzenes, they are remarkable low in the oxidation rate and very poor in the selectivity as compared with secondary alkyl group-substituted benzenes. Such tendency of the secondary alkyl group-substituted methylbenzenes becomes remarkable as the number of the methyl group increases. On account of this, a hydroperoxide has not been obtained from secondary alkyl group-substituted methylbenzenes, at a high efficiency. In order to eliminate such drawback, it has been demanded to develop a process for preparing a hydroperoxide from the above-mentioned methylbenzenes at a higher oxidation rate and a higher selectivity.